Delay blowback mechanism for firearms

ABSTRACT

A gun breechblock of less weight than would be required for purely inertial delay of breech opening under blowback action, is subjected to additional delay action derived from compressive bowing of a backup leaf spring which provides an initially high and progressively decreasing resistance to the blowback.

United States Patent Inventor Harold A. Schlapia, Jr.

1258 N. Fuller Ave., West Hollywood, Calif. 90046 App]. No. 817,844

Filed Apr. 21, 1969 Patented Jan. 12, 1971 DELAY BLOWBACK MECHANISM FOR FIREARMS 4 Claims, 3 Drawing Figs.

[1.8. CI 89/194, 89/199, 267/165 Int. Cl F41d 1/08, F4ld 1 1/ 12 Field of Search 89/180,

[56] References Cited UNITED STATES PATENTS 814,749 3/1906 Trabue 89/199UX 2,772,086 11/1956 Foster 267/164 Primary ExaminerBenjamin A. Borchelt Assistant Examiner-Stephen C. Bentley Anorney- Lynn H. Latta ABSTRACT: A gun breechblock of less weight than would be required for purely inertial delay of breech opening under blowback action, is subjected to additional delay action derived from compressive bowing of a backup leaf spring which provides an initially high and progressively decreasing resistance to the blowback.

PATENTEUJANQIQH 35 541077 1N VENTOR.

HAROLD A. JCH AHA, Je.

"ATTORNEY- DELAY BLOWBACK MECHANISM FOR FIREARMS THE PRIOR ART Delay opening breech mechanisms with straight blowback (purely inertial) delay action have been utilized heretofore, but have the disadvantage of requiring excessive breechblock weight. Hence the vast majority of existing small arms for high-powered cartridges utilize locked breech mechanisms, but these have the disadvantage of being expensive to manufacture. I

OBJECT OF THE INVENTION The general object of the invention is to provide a delay breech-opening mechanism suitable for high-power cartridges, which is both lightweight and inexpensive. Further objects are to provide a delay mechanismwhich:

1. will provide maximum resistance (and delay) in the initial stage of breech opening, and accelerating decay of resistance to an extremely low value in the final stage of opening;

2. will achieve this by combining moderate inertial resistance with progressivelydeclining spring resistance;

3. will eliminate the need for a breech-locking mechanism 4 l is of light weight construction; and 5. is inexpensive to construct.

DESCRIPTION These and other objects will become apparent in the following specification and appended drawing, in which:

FlG. I is a schematic diagram of a blowback delay mechanism embodying the invention, in the instant of firing;

FIG. 2 is a schematic diagram of the same in a final stage of operation after cartridge discharge; and

H6. 3 is a schematic diagram of the same in a final stage of operation.

Referring now to the drawing in detail, I have shown therein, schematically, the essential elementsof the invention, comprising a breechblock A normally closing the breech at the rear end of a barrel B, the breechblockbeing slidable in a breech chamber. C at the rear end of barrel B. The breechblock A is subjected to compressive force applied to its rear end by a pair of leaf springs D which normally hold the breechblock in closing relation to breech l0. Springs D in their normal positions (FIG. I) are slightly'bowed but nearly initially high resistance to breech opening which is added to the inertia of breechblock to provide a maximum holding force at the instant of firing a cartridge 11, of sufficiently high resistance to opening movement of breechblock A to provide any desired delay of breech opening so as to enable the projectile 12 of cartridge 11 to be driven, by the propelling gases to the muzzle 13 of barrel B (FIG. 2) before the breechblock A has yielded to far rearwardly under back pressure of the propelling gases. The initial spring resistance may be any selected proportion of the total resistance to breech opening afforded by the collective action of spring loading and breechblock inertia. A means for adjustably setting the springs to varying degrees of initial bowing may be in the form of an ellipsoidal (elliptical cross section) cam 25 having end trunnions 26 projecting through opposite sides of the wall of breech chamber C and rotatably mounted therein with a snug fit such as to hold the cam in selected positions of adjustment. On the projecting outer end of one of the trunnions is secured an adjusting knob 27, for manual rotary adjustment of the cam. Adjustment of spring loading allows for variations in loaded ammunition, its proportion of resistance being a very substantial one. The breechblock resistance can be reduced to what ever extent required.

An important aspect of the invention is the highly negative rate of springs D due to their nearly straight normal condition and their deflection to increasingly bowed condition as they yield to the rearward movement of breechblock A, to a collalpsed condition at the final stage of breech opening (FIG. 3). T e resistance provided by the springs decays to progressively lower values as the springs become progressively more bowed until, at their collapsed condition (FIG. 3) their resistance is only a small fraction of its initial value. Correspondingly, the initial resistance of breechblock A progressively decreases (with accelerating movement) from its maximum value in its initial static condition, to a minimum value at its highest velocity.

Springs B may be arranged to engage the lateral wall of chamber C (H6. 3) to limit their bowing movement and to function as a stop, preventing further recession of breechblock A.

The rear ends of springs B are supported against a suitable abutment l5 (e.g. rear wall of chamberC) and are positioned by suitable means such as having their ends engaged in sockets 16 and 17 in the rear end of breechblock A and in abutment 15 respectively.

lt is to be noted that chamber C is provided with a conventional cartridge case ejection opening 18 which is closed by breechblock A until the latter has reached a final stage of recession in which opening 18 is uncovered and the spent case is ejected. v

The drawing is largely schematic. It does not represent conventional proportioning (e.g. as between barrel length and other dimensions) and it should be understood that other con ventional elements of firearm structure, forming no part of the present invention, will be embodied in a gun equipped with the invention, but are ommitted from the drawing herein to avoid obscuring the invention and because their disclosure is not necessary to an understanding of the-invention.

lclaim:

l. A blowback delay mechanism for a firearm having a barrel, a breech at the rear end of said barrel, and a breech chamber extending rearwardly from said breech, said delay mechanism comprising: a. a breechblock slidable axially in said chamber, said breechblock having inertia insufficient in itself to sufficiently delay breech opening in response to firing of a cartridge of selected power; b. 'an abutment in said chamber behind said breechblock; and c. a leaf spring extending between said abutment and the rear end of said breechblock, said spring being positioned substantially parallel to the axis of sliding movement of said breechblock and engaged between said abutment and'breechblock under coinpression, with a resistance to receding movement of said breechblock which is initially of relatively high value and which decays during lateral bowing of said spring enforced thereon by receding movement of said breechblock in response to the back pressure of cartridge firing, to a relatively low value at the rearward limit of said receding movement, said spring resistance supplementing the inertia of said breechblock in delaying breech opening in response to said back pressure.

2. A blowback delay mechanism as defined in claim I, wherein said spring is normally slightly bowed so as to yield with further bowing in response to breechblock pressure against its forward end.

3. A blowback delay mechanism as defined in claim 2. wherein said spring is normally nearly straight so as to provide maximum resistance at the beginning of its receding movement.

4. A blowback delay mechanism as defined in claim I. wherein there are two of said springs, arranged to bow outwardly away from one another. 

1. A blowback delay mechanism for a firearm having a barrel, a breech at the rear end of said barrel, and a breech chamber extending rearwardly from said breech, said delay mechanism comprising: a. a breechblock slidable axially in said chamber, said breechblock having inertia insufficient in itself to sufficiently delay breech opening in response to firing of a cartridge of selected power; b. an abutment in said chamber behind said breechblock; and c. a leaf spring extending between said abutment and the rear end of said breechblock, said spring being positioned substantially parallel to the axis of sliding movement of said breechblock and engaged between said abutment and breechblock under compression, with a resistance to receding movement of said breechblock which is initially of relatively high value and which decays during lateral bowing of said spring enforced thereon by receding movement of said breechblock in response to the back pressure of cartridge firing, to a relatively low value at the rearward limit of said receding movement, said spring resistance supplementing the inertia of said breechblock in delaying breech opening in response to said back pressure.
 2. A blowback delay mechanism as defined in claim 1, wherein said spring is normally slightly bowed so as to yield with further bowing in response to breechblock pressure against its forward end.
 3. A blowback delay mechanism as defined in claim 2, wherein said spring is normally nearly straight so as to provide maximum resistance at the beginning of its receding movement.
 4. A blowback delay mechanism as defined in claim 1, wherein there are two of said springs, arranged to bow outwardlY away from one another. 